The invention relates to methods of localized repair to damaged thermal barriers.
The blade sets of high-pressure turbines in aeroengines are exposed to an environment that is very aggressive. In general, such parts are coated by an oxidation protection coating and by a thermal barrier coating. The thermal barrier coating serves to insulate the underlying part thermally so as to enable it to be maintained at temperatures where its mechanical performance and its lifetime are acceptable.
Certain zones of the system may be damaged in service at high temperature by erosion, by particle impact, by oxidation, by corrosion, and by calcium and magnesium aluminosilicates (CMAS). The photographs provided in FIGS. 1 and 2 show the appearance of blades that have been damaged in service. Such degradation can lead to local disappearance of the thermal barrier layer and even of the underlayer, leading to oxidation of the underlying part.
At present, in order to reconstitute a thermal barrier, it is known to remove the entire thermal barrier coating (even the zones that are not damaged) of parts and then to make a new thermal barrier system. In certain circumstances, parts having a thermal barrier that has been damaged may even need to be discarded.
There exists a need to improve the length of time for which parts coated by thermal barriers can be used.
There exists a need to simplify and reduce the cost of methods of repairing damaged thermal barriers.
There also exists a need to have new methods of repairing damaged thermal barriers.